Magnetic device



Mud! 1931- D. D. MILLER ET AL 1,795,499

MAGNETIC DEVICE Filed May 31, 1929 2 Sheets-Sheet 1 D. 0. Ma. 1. El?wvmrms J FHA 7' r ATTOR/VE) March 10,1931. Q 0. n. MILLER ET AL1,795,499

MAGNETIC DEVICE Filed May 31, 1929 2 Sheets-Sheet 2 66 4 I 3 35 5 63. ii25 45 46 '4/ 45 Q x /5 N 43 44 N 7- 4'2 545 V 2 47 V 74 3 57 2 24 29 3 UL5 0 0 MLLER m mmfis E. J PEA r T ATTORNEY Patented Mar. 10, 1931 UNITEDSTATES PATENT OFFICE DANIEL D. MILLER AND EDWARD J. PRATT, OF NEW YORK,N. Y., ASSIGNORS T0 BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEWYORK, N. Y., A CORPORATION OF NEW YORK MAGNETIC DEVICE Application filedMay 31, 1929.

This invention relates to magnetic devices and particularly to suchdevices when used for measuring service in telephone systems.

The object of the invention is to increase the sensitivity, to improvethe efficiency and to insure a greater reliability of operation ofelectromagnetic measuring devices.

l-Ieretofore, various types of telephone substation meters have beenproposed for measuring the amount of use a subscriber makes of histelephone. Many of these are open to the objection that they are notenicient enough to operate on the low operating currents. Others are notdependable in their operation. till others are delicate in cornstruction and subject to damage in handling and shipp ng.

iccording to the present invention these objections are overcome bymeans of an instrument comprising two permanent bar magnets having theirrespective ends interconnected by two electromagnets, saidelectromagnets having restrictions intermediate their ends "1 whichenergizing coils are .vonnd, together with an armature comprising twoparallel pieces, one above and the other below said coils, and arrangedto oscillate in such a manner as to overlap the restricted portions ofsaid bars and the unrestricted portions on either side of therestrictions.

A. feature of the invention is a device of this character in which thearmature shaft carries a member loosely mounted for movement relative tothe armature and having a yielding connection between the armature andsaid member and a friction element between said parts to prevent reboundof the armature as it moves to its extreme position.

Another feature is a magnetic device in which the armature is so shapedas to produce a slight amount of magnetic bias when the armature is ateither of its extreme positions. This prevents the armature fromdrifting due to vibration and causing a false operation of the device.

he accompanying drawings show an embodiment of the invention arrangedfor use a a telephone subscribers station to record the amount ofconversation for which the sub- Serial No. 367,490.

scriber is to be charged. Fig. l is a front view of the recordinginstrument, the outside casing having been removed; the face of theindicating mechanism has been cut away to show the driving ratchet andgears. Figs. 2 and 3 are views of the armature whose movement back andforth actuates the indicating mechanism. Fig. 4.- is a front view withthe indicating mechanism and armature removed; the mid-position of thearmature is shown by the broken lines. Fig. 5 is a top view with theoutside casing cut away, and Fig. 6 is a rear sectional view which showsthe structure of the electromagnets and the cork stops which limit themovement of the armature. The embodiment of the invention as disclosedby Figs. 1 to 6, inclusive, will now be described in detail.

Referring to Figs. 4 and 5, the operating mechanism of the recordingdevice is enclosed in a rectangular box-like casing which consists ofthe shell 2 and base plate 69. Being made of magnetic metal, the casingshields the mechanism from external magnetic interferences. The base 69is arranged to be fastened by screws to a wall or other vertical support, and has a hole in its middle portion through which the telephonewires may be brought in for connection to wiring lugs such as 64; byterminal screws such as 65. The wiring lugs are mounted on the terminalblock 63 which is fastened by screws to a mounting plate 1. Twohinge-like devices 61 and 62 are fastened to the right-hand edge of thebase plate 69 and are engaged by slots in the shell 2. The head of thescrew 67 which extends from the front of the casing to the base plate 69is formed into an eye 68 which may be sealed to a similar eyepermanently connected to the front of the casing so as to preventtampering with the wiring after installation. The mounting plate 1 isrigidly held inside of the shell 2 by screws such as 66 which are spacedaround the edge of the shell. The installer has no access to theoperating mechanism without breaking the manufacturers seal which isplaced on one of the screws which hold the mounting plate 1 in the shell2.

A non-magnetic, many-limbed, metallic framework 3 is rigidly attached byscrews to the mounting plate 1 and upon this framework the recordingmechanism is assembled. Two permanent magnets 12 and 14 are fastened tothe framework 3 by the clamping plates 11 and 13 and screws 15, 16, 17and 18 as shown in Figs. 1, 4 and 5. The upper ends of these magnets arelike magnetic poles and are designated N. A magnetic bar 42 ofrectangular cross section extends between the upper. ends, N poles, ofthe bar magnets 12 and 14 and a similar bar 52 extends between the lowerends, S poles, of these magnets. These bars are held by the screws 15,16, 17 and 18 between the ends of the bar magnets and the framework 3.The bar 42 is the cor of electromagnet 41 and the bar 52 is the core ofelectromagnet 51. The winding of the magnet 41 is limited at its ends bythe cop per collars 43 and 44 and the winding of the electromagnet 51 islimited at its ends by the copper collars 53 and 54, as shown in Figs.4, 5 and 6. Pole pieces 45 and 46 are fastened by the screw 49 to thefront rear, respectively, of the core 42. The pole piece 45 .occupiesthespace between the upper end of the bar magnet 12 and the copper collar43 and the pole piece 46 occupies the space between copper collar 43 andthe corresponding end of the supporting limb of the framework 3. In asimilar manner pole pieces 4'? and 48 are fastened by the screw 50 tothe front and rear of the core 42. The pole piece 47 occupies the spacebetween the copper collar 44 and the upper end of bar magnet 14 and thepole piece 48 occupies the space between the copper collar 44 and thecorresponding end of the supporting limb of the framework 3. Thepolepieces and 56 and the pole pieces 57 and 58 are similarly fastenedby screws 59 and 60 to the core 52 which extends between the S poles ofthe bar magnets 12 and 14, as shown in Fig. 4. The winding of theelectromagnet 41 is connected by leads 40, shown in Fig. 1, to wiringlugs on the back of the terminal block 63. The winding of theelectromagnet 51 is similarly connected to lugs on the terminal block63.

The armature whose movement is controlled by the electromagnets 41 and51 con sists of the two magnetic pieces 21 and 22 and the non-magneticspacing block 26, all of which are rigidly fastened together by thescrews 27 and 28, as shown in Figs. 1, 2, 3 and 5. The armature ismounted on a shaft which consists of a middle section 31, which extendsthrough the pieces 21 and 22 and the block 26, and the two end sections32 and 33. These end sections which have a greatly reduced diameter, ascompared with the middle section 31, extend into bearings 35 and 37which are supported by the framework 3, as shown inFig. 5. The bearingsare so shaped that the normal bearing surface is limited to the extremeends of the sections 32 and 33.

By reducing the diameter of the bearing surface of the shaft the forcenecessary to overcome the bearing friction in moving the armature isgreatly reduced. Sleeve-like portions of the bearings, which overlap theends of the unreduced section of the shaft 31 and have an insidediameter slightly larger than the section 31, limit the flexure of theend sections'of the shaft, when subjected to shock such as might beexperienced in shipping, to a safe limit. Thus the peculiar constructionof the shaft and bearings results in a very sensitivebut ruggedinstrument. The bear ing 37 is fixed but the bearing 35 is adjustableand the lock nut 36 holds it in any given position.

The armature pieces 21 and 22 and the spacing block 26 are made heavy sothat the armature will not respond to momentary impulses even thoughthey greatly exceed the normal actuating force. The copper collars 43and 44 encircling the core 42 and the copper collars 53 and 54encircling the core 52 help to retard any movement of the armature inresponse to momentary impulses of current through the wi dings of theelectromagnets or to mechanical shock.

The movement of the armature is limited by cork stop pieces 38 and 39which are fastened to the framework 3 by clamps 19 and 20 and screws 15and 17. See Figs. 1, 5 and 6. The non-ma netic damping bar 23 isattached by the spiral spring 24 and lug 29 to the upper end of thearmature piece 21, and by the spiral spring 25 and arm 30 to the lowerend of the armature piece 21. The damping bar 23 which is looselypivoted on the shaft 31 is held by the two springs 24 and 25 against thefiatsurface of a piece of cork 34 which is affixed to the rear side ofarma ture piece 22. When the armature strikes either one of the corkstop pieces 38 or 39, the damping bar, springs, and corl: 34 areeffective to prevent rebound and hold the armature in either of itsextreme positions until moved to the other by current through thewindings of the electromagnets. This arrangement prevents falseoperation of the indicating mechanism.

The ends of the armature pieces 21 and 22 are so shaped that with theirupper ends in the extreme left-hand position, viewed from the front ofthe instrdment, their upper right-hand edges are substantially in linewith the copper collar 44; and with their upper ends in the extremeright-hand position, their upper left-hand edges are substantially inline with the copper collar 43. The lower ends of the pieces 21 and 22are similarly shaped. This construction secures the maximum amount ofoverlap between thearmature and the pole pieces 45 and 46, when theupper ends of the armature pieces are in their extreme left-handposition, without any overlap between the armature and the pole surfacepieces 47 and 48; it also secures the maximum overlap between thearmature and the pole pieces 47 and 48, when the upper ends of thearmature pieces are in their extreme righthand position, without anyoverlap between the armature and the pole pieces 45 and 46. Thusconstructed there is a slight magnetic bias which tends to hold thearmature in either of its extreme right or extreme lefthand positions ifonce moved to one of these positions.

The arm 30 which is attached by screws to the lower end of the armaturepiece 21 ex tends toward the indicating mechanism and the driving pawls9 which engage the ratchet 10 are pivoted on the extension of this arm.See Fig. 1. The ratchet 10 and gears 6, 7 and 8 are supported betweenthe plates 4 and 5. The plate 4 is the 'dialplate on which the dials,attached to the shafts of the gears 6, 7 and 8, indicate the amount ofconversation, for which the subscriber, at whose station the device isinstalled, is to be charged. The three dials respectively indicatethousands, hundreds and tens. The dial plate 4 is visible from the frontof the instrument through a glass window in a rectangular opening in thefront of the shell 2,. as shown in Fig. 5. The glass '70 cannot beremoved from the outside without being broken.

For the purpose of describing the actuation of the armature assume thatthe recording device has been installed at a telephone subscribersstation, the windings of both electromagnets 41 and 51 being connectedin series with the line which connects the telephone instrument to thecentral oflice. lVith no current flowing over the line and through thewindings of the electromagnets, the mag netic flux is so distributed, ashereinbefore explained, as to hold the armature pieces 21 and 22 ineither one of their extreme positions if originally placed in one ofthese positions. As viewed from the front of the in strument one branchof the circuit for this flux may be traced from the N pole of the bar 12through the left-hand end of core 42, through the pole piece 45,armature piece 21, pole piece and through the left-hand end of core 52to the S pole of bar 12; another branch may be traced from the N pole ofbar 12, through core 42, pole piece 46, arma ture piece 22, pole piece56 and core 52 to the S pole of bar 12; another branch may be tracedfrom the N pole of bar 14, through the right-hand end of core 42, polepiece 47, armature piece 21, pole piece 57, right-hand end of core 52 tothe S pole of bar 14; and a fourth branch may be traced from the N poleofbar 14, through core 42, pole piece 48, armature piece 22, pole piece58 and core 52 to the S pole of magnet 14.

\Vhen a connection has been established between this station and someother station, for which the subscriber at this station should becharged, the central ofiice equipment causes equally spaced reversals ofthe talking current over the line through the windings of theelectromagnets 41 and 51 and the subscribers telephone instrument. lViththe talking current flowing in one direction the field of theelectromagnet 41 is such as to strengthen the flux through the polepieces 45, 46, 57 and 58 and weaken the flux through the pole pieces 47,48, 55 and 56; if not already with their upper ends in the extremeleft-hand position as viewed from the front of the instrument thearmature pieces will be moved to that position. If the current isreversed over the line the flux through pole pieces 45, 46, 57 and 58becomes Weaker than the flux through the pole pieces 47, 48, 55 and 56so as to cause the upper ends of the armature pieces 21 and 22 to bemoved to their extreme right-hand position. Thus each reversal of thetalking currents moves the armature pieces 21 and 22 to the otherposition from that in which they were resting and in so doing thedriving pawls 9 advance the ratchet one step to re cord one conversationunit of time for which a charge is to be made.

The copper collars 43 and 44 which surround the core 42 at the ends ofthe winding of the electromagnet 41 and the copper collars 53 and 54which surround the core 52 at the ends of the winding of theelectromagnet 51, act as short-circuited secondary windings of atransformer to reduce the effective impedance of the windings of theelectromagnets so that the quality of the transmission over thesubscribers line will not be seriously affected by the installation ofthe register.

What is claimed is: a

1. The combination in an electromagnetic device of two permanentlymagnetized bars, two electromagnetic bars interconnecting the respectiveends of said first mentioned bars, said electromagnetic bars havingrestrictions intermediate their ends, energizing coils in saidrestrictions, an armature comprising two parallel pieces, one on oneside and one on the other side of said coils, and arranged to oscillatein such manner as to overlap the restricted portions of said bars andthe unrestricted portions, and means driven by said armature.

2. The combination in an electromagnetic device of a permanent magnet,an electromagnet having an energizing winding thereon, a shaft, anoscillating armature mounted on said shaft and cooperating with saidmagnets, a member loosely mounted on said shaft for movement relative tosaid armature, a yielding connection between the armature and saidmember, and a friction element between said armature and member toprevent said armature from rebounding.

3. The combination in an electromagneti device of a core, a coil woundaround said core, and a copper collar surrounding said core at the endof said coil for reducing the impedance of said coil to voice frequencycurrents.

4. The combination in an electromagnetic device of permanentlymagnetized and electromagnetic members, a core for each of saidelectromagnetic members extending be:- tween the poles of saidpermanently magnetized members, a coil for each of said electromagneticmembers wound around said core, and a collar of non-magnetic metalsurrounding said core at the end of said coil for reducing the impedanceof said coil to voice frequency currents.

5. The combination in an electromagnetic device of permanentlymagnetized members, electromagnetic members, the core of each of saidelectromagnetic members extending between like poles of the permanentlymagnetized members, the coil of each of said electromagnetic membersbeing wound around the middle portion of the associated core, anarmature included in the magnetic circuits of said permanent magnets andarranged to move back and forth about an axis normal to the plane ofsaid permanent magnets, and means actuated by said armature.

6. The combination in an electromagnetic device of two permanent barmagnets, two electromagnets whose cores extend respectively between likepoles of said bar magnets, the coil of each of said electromagnets beingwound around the middle portion of the associated core, an armaturecomprising two parallel pieces extending respectively from the sides ofone of said coils to the corresponding sides of the the other of saidcoils, said armature being arranged to move back and forth about an axisextending through the middle of said pieces normal to the plane of saidbar magnets, and means actuated by said armature.

7. The combination in an electromagnetic device of two permanentlymagnetized members, magnetic bars extending between like poles of saidpermanent magnets, a coil wound around the middle portion of each ofsaid magnetic bars to form an electromagnet, pole pieces common to saidpermanent and electromagnetic members, an armature arranged to move backand forth on an axis which passes through its middle normal to the planeof said permanent magnets, means for limiting the movement of saidarmature in both directions so that in either of its extreme positionsone end of said armature overlaps one of said coils and the pole piecesassociated with the N pole of one of said per maneiit magnets and theother end of said armatureoverlaps the other of said coils and the polepieces associated with the S pole of the other of said permanentmagnets, and means actuated by said armature.

8. The combination in an electromagnetic device of permanentlymagnetized and electromagnetic members, a .core for each of saidelectromagnetic members extending between like poles of said permanentlymagnetiz'ed members, a coil for each of said electromagnetic memberswound around the middle portion of the associated core, an armature, ashaft extending through the middle of said armature normal to the planeof said permanently magnetized members, bearings supporting the ends ofsaid shaft, a member loosely mounted on said shaft, retractile springslinking the ends of said member to the ends of said armature, a frictionelement afiixed to said armature for retarding the angular motion ofsaid'member relative to said armature, and armature stop pieces forlimiting the movement of said armature.

9. The combination in an electromagnetic device of permanentlymagnetized and electromagnetic members, a core for each of saidelectromagnetic members extending between like poles of said permanentlymagnetized mmebers, a coil for each of said electromagnetic memberswound around the middle portion of the associated core, copper collarssurrounding each of said cores to reduce the impedance of said coils andto retard a change in the position of said armature, pole pieces commonto said permanently magnetized and electromagnetic members affixed tothe sides of said cores between the ends of said coils and the poles ofsaid permanently magnetized members, an armature comprising two piecesarranged to move back and forth about an axis through its middle,non-metallic stop pieces limiting the movement of said armature, andmeans actuated by said armature.

10. The combination in an electromagnetic device, of a permanent magnet,an electromagnet having an energizing winding thereon, a copper collarsurrounding said core at the end of said winding for reducing theimpedance of said winding to voice frequency currents, a shaft, anoscillating armature mounted on said shaft and cooperating with saidmagnets, a member loosely mounted on said shaft for movement relative tosaid armature, a yielding connection between the armature and saidmember, and a friction element between said armature and memher toprevent said armature from reboundmg. I

11. The combination in an electromagnetic device of permanent andelectromagnetic members, said electromagnetic members havingrestrictions therein, energizing coils in said restrictions, a coppercollar surrounding the core of each of said electromagnetic members forreducing the impedance of said energizing coil to voice frequencycurrents, and

an armature mounted to oscillate in such a manner as to overlap therestricted and unrestricted parts of said electromagnetic members oneither side of said restrictions, the sides of said armature being soshaped that when said armature is in its extreme position one side ofthe armature is substantially parallel to the edge of the coilrestriction.

12. The combination in an electromagnetic device of permanentlymagnetized members, electromagnetic members, the core of each of saidelectromagnetic members extending between like poles of the permanentlymag netized members, the coil of each of said electromagnetic membersbeing wound around the middle portion of the associated core, a collarof non-magnetic metal surrounding the core of each of saidelectromagnetic members for reducing the impedance of said coils tovoice frequency currents, an armature included in the magnetic circuitsof said permanent magnets and arranged to move back and forth about anaxis normal to the plane of said permanent magnets, and means actuatedby said armature.

13. The combination in an electromagnetic device of two permanent barmagnets, two electromagnets whose cores extend respectively between likepoles of said bar magnets, the coil of each of said electromagnets beingwound around the middle portion of the associated core, an armaturecomprising two parallel pieces extending respectively from the sides ofone of said coils to the corresponding sides of the other of said coils,said armature being arranged to move back and forth about an axisextending through the middle of said pieces normal to the plane of saidbar magnets, a collar of non-magnetic metal surrounding the core of eachof said electromagnets for reducing the impedance of said coils and toretard a change in the position of said armature, and means actuated bysaid armature.

In witness whereof, we hereunto subscribe our names this 28th day ofMay, 1929.

DANIEL D. MILLER. EDWARD J. PRATT.

